Mat 29, 1914] 



SCIENCE 



789 



on the desk to consult from time to time upon 

 questions of exact fact. The interest in ttis 

 line of investigation is so intense at present 

 that it is perfectly obvious that enough new- 

 facts will be accumulated in another season to 

 warrant the adding of several chapters. 



L. O. HOWAED 



The Progress of Scientific Chemistry in Our 



Own Times. By SiE William A. Tilden. 



New York, Longmans, Green and Co. 1913. 



Second edition. 15 X 20 cm. Pp. v + 366. 



Price, $2.25 net. 



The period covered by the book is from 1837 

 to the present. The first date was selected be- 

 cause Queen Victoria then came to the throne, 

 while the scientific justification might be that 

 at that time the influence of Liebig's teaching 

 was beginning to be felt. After the usual pre- 

 liminary chapter on Lavoisier, Cavendish, Dal- 

 ton and Berzelius. we get to the book proper. 

 We start with the conservation of energy and 

 Joule's determination of the thermodynamic 

 equivalent of heat. This leads at once to 

 Hess's law of thermochemistry, to the experi- 

 ments of Julius Thomsen, to Berthelot's 

 enunciation of his principle of maximum 

 work, and to St. Claire Deville's work on dis- 

 sociation. The second chapter — which per- 

 haps should have been the first — deals with the 

 distribution of the chemical elements and the 

 recognition of them by the chemist. This, 

 of course, involves Bunsen and Kirchhoff's 

 work on spectrum analysis, the discovery of 

 argon by Rayleigh and Eamsay, and the isola- 

 tion of the other noble gases by Ramsay. The 

 elements being given, the third chapter deals 

 with the determination of the atomic weights, 

 including the theoretical reforms of Canniz- 

 zaro and the experimental researches of 

 Dumas, Stas and others. The work of Ger- 

 hardt, Laurent and others on types is also 

 taken up in this chapter. This seems a mis- 

 take because the work has to be discussed 

 later in its proper place. The justification 

 for its inclusion at this point seems to be that 

 it was necessary in order to determine the 

 atomic ratios of carbon to hydrogen and oxy- 

 gen. While this is doubtless true historically. 



it would have been more artistic to have passed 

 over this difliculty gracefully and thus to have 

 avoided repetition. 



Once we have the atomic weights deter- 

 mined, we are confronted with Prout's hypoth- 

 esis. The third edition will undoubtedly con- 

 tain the account of the resurrection of this 

 hypothesis by Rutherford, but only a prophet 

 could have included that in this edition. 

 After Prout's hypothesis has been disposed of, 

 the remainder of the fourth chapter is de- 

 voted to Mendeleefi's periodic law and its de- 

 velopments. The question of constitutional 

 formulas comes up in the fifth chapter, which 

 carries us through the work of Kekule. The 

 fruitfulness of Kekule's conception is brought to 

 our minds clearly in the account of synthetical 

 organic chemistry in the sixth chapter. In 

 the seventh chapter we have Pasteur's work on 

 optically active substances, and the theory of 

 stereochemistry as developed by van't HofE 

 and Le Bel. The next step, historically and 

 logically, is from the problem of the molecular 

 structure to that of chemical affinity, and the 

 eighth chapter is consequently devoted to a 

 discussion of electricity and chemical affinity. 

 Up to this point, the treatment has been 

 logical and coherent; but the ninth chapter is 

 an intercalated one on the liquefaction of 

 gases. There is no conceivable reason for in- 

 troducing this chapter at this point except 

 that the author perhaps did not know where 

 else to put it. As a matter of fact it should 

 have come in just before the account of Ram- 

 say's isolation of the noble gases of the at- 

 mosphere. Presumably it was not put there 

 because the author wished to discuss the lique- 

 faction of helium, which he could not do until 

 he had introduced helium to his audience. 

 He should however have discussed the general 

 problem of the liquefaction of gases as an in- 

 troduction to Ramsay's work and he could 

 then have taken up the liquefaction of helium 

 as a special fact under the general properties 

 of helium. 



If this had been done, we should have passed 

 directly from the chapter on chemical afSnity 

 to that on radioactivity. The loose ends are 

 gathered up in a final chapter which includes 



